1. Field of the Invention
The present invention relates to an improved catalyst composition for the formation of gel-free copolymers and terpolymers of isobutylene and one or more dienes having an Mn of about less than 500,000, a mole % unsaturation of about 0.1 to about 45, and a polydispersity value of about 2.5 to about 30, wherein the mixture of isobutylene and diene monomers and a cosolvent are contacted with the catalyst composition at polymerization conditions (0.degree. to -100.degree. C.) wherein the improvement includes the hydrocarbon soluble catalyst composition being formed from the reaction product of a material of the formula: EQU R.sub.m AlX.sub.3-m
wherein m is an integer of from 1 to 3 inclusive, R is the same or different alkyl radical of straight or branched chain structure of from 1 to 7 carbons and X is the same or different halogen selected from the group consisting of chlorine and bromine, and a halogen containing material which is Y moles of halogen, halogen acid, or mixed halogen per mole of aluminum compound wherein the halogen is selected from the group consisting of chlorine and bromine wherein the molar ratio of the formed catalyst composition to the monomer is critical by selecting at about 0.00001 to about 0.001 in order to obtain the desired elastomeric co- and terpolymers. The molar ratio of the halogen containing material to the R.sub.m AlX.sub.3-m used in forming the catalyst is critically selected at about 0.014 to about 0.15. This improved catalyst composition is soluble in the inert solvent and permits the formation of high quality elastomeric products at improved polydispersity levels and higher % conversions.
2. Description of the Prior Art
Aluminum compounds are widely used as polymerization catalysts. Aluminum chloride is commonly used to initiate cationic polymerizations but it has the disadvantage of little or no solubility in many desirable hydrocarbon systems especially where homogeneous polymerizations are required. Aluminum bromide which is soluble in hydrocarbons, has limited utility as such in a number of desirable systems. Alkylaluminum dihalides are generally less reactive than the aluminum halides but offer the advantage of excellent hydrocarbon solubility. To enhance their reactivity, they are frequently used together with cocatalysts. Proton donators like the halogen acids, are placed in the polymerization medium and are said to be ionized by the aluminum compound thereby releasing protons to initiate polymerization. Halogens and organic halogen compounds are also ionized in situ to initiate cationic polymerization. In the case of dialkylaluminum halides and aluminum alkyls, such cocatalysts are required since these compounds are not generally active in themselves. Also compounds like dialkylaluminum iodides and alkylaluminum diiodides, which are generally not effective initiators in and of themselves, have been utilized with halogen cocatalysts, such as iodine, to initiate the polymerization. The iodine must be present in the polymerization medium and is ionized by the aluminum component, the ions initiating the polymerization. This is a good illustration of cocatalysis since neither the starting alkylaluminum iodides nor the product aluminum iodide is a catalyst by itself so the cocatalysts must be present in the polymerization medium.
The catalyst systems of the instant invention differ markedly from those of the prior art. The halogens, halogen acids, interhalogen compounds and organic halogen compounds are not used as cocatalysts but instead are prereacted with the organic aluminum compound to generate novel catalyst species which are hydrocarbon soluble and can be utilized in cationic polymerization systems. These catalysts are generally more reactive and give higher molecular weights than the corresponding organoaluminum compounds from which they are derived. Furthermore, the prereacted catalysts of the instant invention give products superior to the polymerization products obtained using halogens, halogen acids, interhalogen compounds or organic halides as cocatalysts.
Numerous prior art examples using cocatalysts are extant. These are clearly distinguishable from the catalysts of the instant invention. the halides, etc. of the prior art are used either in situ as cocatalysts or as complexing agents.
U.S. Pat. No. 2,220,930 teaches the manufacture of polymers using catalysts such as dialkylaluminum halides or alkylaluminum halides, generally represented as MX.sub.m R.sub.n where M represents aluminum, gallium or boron, X represents halogen, R represents a monovalent hydrocarbon radical, m or n represent integers 1 to 2 inclusive, and m+n=3. The catalyst can also be a complex of the above compounds with inorganic halides (e.g. NaCl) or with ammonia or amines. In practice, U.S. Pat. No. 2,220,930 utilized either dialkylaluminum halides or alkylaluminum dihalides alone or in a mixture of equal parts which is commonly known as the sesquihalide. The polymers of isobutylene obtained were low molecular weight resins.
U.S. Pat. No. 2,387,517 relates to the manufacture of polymers prepared by the copolymerization of various unsaturated compounds in the presence of catalysts of the type MX.sub.m R.sub.n where M represents aluminum, gallium, or boron, X represents a halogen, R represents a monovalent hydrocarbon radical, m or n represent integers from 1 to 2 inclusive and m+n=3. The invention is particularly directed to the formation of curable rubber-like products by the copolymerization of isobutylene with low molecular weight diolefins, especially those having 4 to 6 carbon atoms. The products are described as ranging in molecular weight from 1000 to 3000 up to 300,000 or higher. However, the type of molecular weight is not indicated (most likely viscosity average molecular weight) nor is an actual polymer approaching 300,000 molecular weight prepared. The composition used as catalysts in the above two related cases are not prepared by prereacting an alkyl aluminum halide with halogens, halogen acid or interhalogen compounds of the instant invention and do not suggest the superiority which the instant compositions demonstrate as catalysts.
U.S. Pat. No. 2,388,428 relates to an improved method for affecting organic chemical reactions by generating Friedel-Crafts metal halide catalysts in situ. It teaches dissolving an organoaluminum compound in a hydrocarbon reactant being charged to the process and contacting said solution with an excess of hydrogen halide in a reaction zone under hydrocarbon conversion conditions whereby an aluminum halide catalyst is generated in situ and the conversion reaction is affected. The hydrogen halide is added in excess (in an excess over the amount required to completely convert the organoaluminum compound to the aluminum halide so as to generate aluminum halide (e.g., AlCl.sub.3) in situ). Such generation of aluminum chloride is described as being subject to greater control and of greater precision than prior art methods of dissolving or suspending the aluminum halide in the reaction mixture. Particular note should be taken of the fact that the catalyst components are not prereacted and then added to the reaction zone, but are reacted in situ. Furthermore, the stoichiometry is quite different from the catalysts of the instant invention. The molar ratio of catalyst to monomer is greater than 0.026 and the cocatalyst to catalyst ratio is greater than 4.4. The use of the catalyst of U.S. Pat. No. 2,388,428 for the purposes of polymerization is not taught as the examples are directed solely to isomerization and alkylation at temperatures of 10.degree. C. to 77.degree. C.
U.S. Pat. No. 3,349,065 teaches an improved catalyst system for producing high molecular weight Butyl rubbers, having less than 5.5% mole unsaturation by a slurry process which are highly gelled (4.7 to 70%). The catalyst system comprises a dialkylaluminum halide together with a small but critical amount of an anhydrous hydrogen halide as a promoter (cocatalyst). The amount of anhydrous hydrogen halides used ranges from 0.01 mole to 0.05 mole promoter per mole of dialkylaluminum monohalide. The maximum desirable ratio is 0.05 mole promoter per mole of catalyst. Furthermore, the hydrogen halide is added to a solution containing both the dialkylaluminum chloride and monomer and is not prereacted with said organoaluminum compound as in the method of the instant invention. This patent does not teach, imply or infer the use of a solution process for the formation of gel free elastomers.
U.S. Pat. No. 3,562,804 also described the use of an organoaluminum compound in conjunction with hydrogen chloride or a C.sub.3 -C.sub.7 organic halide compound as promoter to produce low viscosity mastic compositions by a slurry process. Here again, the catalyst and promoter were combined in the presence of monomer and all examples teach the separate addition of catalyst and promoter to the polymerization (monomer) mixture. The catalyst to monomer ratio is at least about 0.001 and the rate of cocatalyst to catalyst is greater than about 3.0.
U.S. Pat. No. 3,850,897 teaches a procedure of the production of polymers and copolymers of isobutylene. The catalyst disclosed is of the general formula RAl(YR')X where Y is an oxygen or sulfur atom together with a wide variety of promoters. The aluminum compounds disclosed in this patent are different from those of the instant invention. Furthermore, the patent in question teaches the necessity of combining catalyst and cocatalyst in the presence of monomers. Stepwise addition of catalyst and cocatalyst to the polymerization medium is demonstrated in the examples. The catalyst to monomer ratio is at least about 0.0038.
U.S. Pat. No. 3,835,079 teaches hot melt compositions comprising styrene, isobutylene copolymer wax and a primary resin. The catalysts employed a system utilizing a primary component alkylaluminum dihalide with a promoter (cocatalyst) such as hydrogen halide. The maximum cocatalyst is 30 mole percent of the primary catalyst. A more limited range, 2.5 to 15% is preferred or 5 to 10% with cocatalysts such as water. The range of compositions is clearly outside that of the instant invention. Furthermore, the promoters are stated to be cocatalysts in this patent while they are consumed in a prior reaction in the instant invention and are not available to serve as cocatalysts.
U.S. Pat. No. 3,560,458 teaches a polymerization process utilizing a catalyst of the type Al(M).sub.2 R where M is an alkyl group and R is alkyl, hydrogen or halogen. It is obvious that the catalyst intended for use is the dialkyl or the monohalide. Experimental procedure reveals a stepwise addition to cocatalyst promoters to a solution containing catalyst in the cationically polymerizable monomer. The molar ratio of catalyst to monomer is at least about 0.007.
British Pat. No. 1,362,295 teaches a catalyst suitable for use in the polymerization of unsaturated compounds and a process for employing such a catalyst. The catalyst used is a two-component substance, the primary component being R.sub.2 AlX wherein R is a hydrocarbon or hydrogen radical, X can be hydrocarbon, hydrogen or halogen. The secondary component is represented as YZ wherein each of Y and Z are the same or different halogen. The component can be present in a ratio of primary to secondary of from 0.1:1 to 1000:1.
All examples contain active cocatalysts, and no criticality for prereaction of components is taught. Furthermore, the ratios of materials involved are such as to not practice the invention of the instant specification and no showing is made of there being a ratio demonstrating superior performance.
Other patents which are non-applicable to the instant invention are: U.S. Pat. Nos. 3,757,000 and 3,560,458; British Pat. Nos. 1,309,131 and 1,157,043; and U.S. patent application Ser. Nos. 635,695 and 737,917.
A major problem in the manufacture of conventional "chlorobutyl" rubbers (isobutylene-isoprene copolymers having less than 8 mole % isoprene) is that in the conventional slurry process the precipitated "chlorobutyl" rubber must be redissolved in a solvent in order to finish the purification of the "Butyl" rubber into a commercial product. Additionally, the present process eliminates the use of halogenated hydrocarbon solvents such as methyl chloride. The resultant "Butyl" rubber from the improved process of the instant invention has improved polydispersity as compared to conventional "Butyl" rubber prepared by a slurry process.